DE102022210096A1 - Process for producing a solid state cell - Google Patents

Abstract

The invention relates to a method for producing a solid cell, wherein at least one electrode layer (12, 22) and at least one separator layer (14) are provided, wherein a molten and ion-conductive adhesive is applied to an interface (20) of the separator layer (14) and/or the Electrode layer (12, 22) is applied, the electrode layer (12, 22) and the separator layer (14) being arranged stacked one above the other, and the interfaces (20) of the separator layer (14) and the electrode layer (12, 22) being formed be joined together in a materially bonded manner using an ion-conductive adhesive bond.

Description

The invention relates to a method for producing a solid cell, in particular for producing a half or mono cell. The invention further relates to a cell component for a solid-state cell as well as a solid-state cell and a solid-state battery.

Motor vehicles that are driven or can be driven electrically or by electric motors, such as electric or hybrid vehicles, usually include an electric motor with which one or both vehicle axles can be driven. To supply electrical energy, the electric motor is usually connected to a vehicle-internal (high-voltage) battery as an electrical energy storage device.

Here and below, a particularly electrochemical battery is to be understood as meaning, in particular, a so-called secondary battery (secondary battery) of the motor vehicle. In such a (secondary) vehicle battery, used chemical energy can be restored by means of an electrical (charging) process. Such vehicle batteries are designed, for example, as electrochemical accumulators, in particular as lithium-ion accumulators.

In order to generate or provide a sufficiently high operating voltage, such vehicle batteries typically have at least one battery module (battery cell module), in which several individual battery cells are connected in a modular manner. Alternatively, a so-called Cell2Pack design is possible, in which the battery cells are connected directly to the vehicle battery, in particular connected in parallel, and are not combined into modules in advance.

The battery cells are designed, for example, as electrochemical (thin) layer cells. The thin-film cells have a layered structure with a cathode layer (cathode) and an anode layer (anode) and with a separator layer (separator) inserted between them. These components are penetrated, for example, by a liquid electrolyte (liquid electrolyte), which creates an ion-conductive connection between the components or a charge equalization. As a rule, several layer cells are arranged stacked one above the other as a cell stack.

The efficiency of cell production is determined by the manufacturing process and the product constitution. One of the most efficient production strategies for conventional thin-film cells is the production of monocells (single cells) using lamination and subsequent stacking to form a monocell stack (single cell stack, single cell stack) with the final number of layers or layers. In this context, “lamination” means that an anode and/or a cathode is joined to one or more laminable separators by applying pressure and temperature. The resulting monocells can be designed, for example, as an anode/separator/cathode/separator stack or as a cathode/separator/anode/separator stack. Due to the product constitution or the structure of the monocells, an alternating cell structure can be created by direct stacking.

Battery cells with a solid electrolyte (solid electrolyte, FE) as a separator layer, hereinafter also referred to as solid state cells or solid cells, have a higher energy storage density than layer cells with liquid electrolytes for the same weight and/or volume. Batteries with solid-state cells are also referred to below as solid-state batteries (FKB) or solid-state batteries.

In solid-state batteries, the (solid-state, solid-state) electrodes or electrode layers, i.e. the cathodes with a catholyte or the anodes (not Li metal) with an anolyte, are stacked to form a cell stack with a solid-state electrolyte (ceramic, glass or glass-ceramic) as a separator . The anolyte and/or the catholyte can consist of a polymer or a ceramic, a glass or a glass ceramic.

The disadvantage is that the separators or solid electrolytes in solid-state cells are comparatively fragile and cannot be melted locally, so that conventional lamination technology cannot be used for the production of solid-state cells. There is currently no continuous production process for producing solid-state monocells.

The invention is based on the object of specifying a particularly suitable method for producing a solid-state cell. In particular, the most effective and efficient production of solid-state cells should be realized. The invention is also based on the object of specifying a particularly suitable cell component and a particularly suitable solid-state cell as well as a particularly suitable solid-state battery.

With regard to the method, the task is solved with the features of claim 1 and with regard to the cell component with the features of claim 4 and with regard to the solid cell the features of claim 6 and with regard to the solid-state battery with the features of claim 7 solved according to the invention. Advantageous refinements and further developments are the subject of the subclaims.

The invention relates to a new cell design for solid-state cells, which makes production much more efficient. The invention relates in particular to the construction of a cell component, in particular a solid half cell or a sandwich cell or a solid monocell (solid single cell) or a monocell stack, in order to realize a production process that is as continuous as possible. However, these half or mono cells are not produced by heating the cell components, as is the case with conventional lithium-ion cells, but rather by using a molten adhesive.

A molten adhesive is understood to mean an adhesive or adhesive agent which is a solid in the dried or hardened state and which changes into a liquid state when heated. The molten adhesive is therefore designed in particular as a hot melt adhesive or hot melt adhesive. The molten adhesive preferably has a comparatively low melting temperature between 25 °C (degrees Celsius) and 50 °C, in particular between 30 °C and 40 °C, for example about 35 °C. The term “approximately” refers in particular to a certain temperature range around the specified temperature value, for example ± 3°. For example, a temperature of approximately 35° is to be understood as (35 ± 3)°, i.e. as a temperature range between 32 ° C and 38 ° C.

Here and below, a (solid) half cell (solid half cell) is to be understood in particular as meaning a cell component with only two cell layers or cell layers. A cell layer or cell layer is to be understood as meaning a cut or cut-to-length (electrode/separator) sheet. The cell layers here have an electrode layer, i.e. a solid or solid electrode, for example a cathode layer or anode layer, and a separator layer, i.e. a solid electrolyte. The electrode layer and the separator layer are stacked one above the other. The half cell is the smallest structural unit or cell component in terms of cell production.

The electrode layer has, for example, an (electrode) active material, a binder, a conductive carbon black and a solid electrolyte. The electrode layer has, for example, an anode or cathode active material as the active material.

For example, graphite (graphite) or lithium-alloying materials such as silicon (Si), zinc (Sn), or lithium titanate are used for an anode. The anode can, for example, simply be formed by a collector (copper/aluminum) on which lithium can deposit. The collector can also be coated, for example the collector can have a nickel coating.

In the case of a cathode, in particular lithium transition metal oxides such as NMC (lithium-nickel-manganese-cobalt oxides) or LMNO (lithium-manganese-nickel oxide) with different stoichiometric ratios, LFP (lithium iron phosphate) or other phosphates such as LMP (Lithium Metal Polymer) is used. For example, (conductive) carbon blacks, graphene, carbon nano tubes (CNT) in the version as single wall (SWCNT) or multi wall (MWCNT) or combinations thereof can be used as conductive additives.

For example, LLZO (lithium-lanthanum-zirconium oxide) or LATP (aluminum-lithium-titanium-phosphate) and their derivatives can be used as separator material for the separator layer.

The next larger structural unit or cell component is also referred to here and below as a sandwich cell. A sandwich cell has three cell layers. Here either an electrode layer is arranged sandwich-like between two separator layers, or a separator layer is arranged sandwich-like between two electrode layers with different polarity, i.e. between an anode layer and a cathode layer.

Here and below, a (solid-state) monocell (solid-state mono-cell) is understood to mean, in particular, an arrangement of two half-cells with different polarities. This means that one half cell has an anode layer and the other half cell has an electrode layer with a cathode layer. The monocells are designed, for example, as an anode/separator/cathode/separator stack or as a cathode/separator/anode/separator stack.

Here and below, a monocell stack is to be understood in particular as meaning a direct alternating arrangement of a number of monocells, i.e. at least two monocells, so that anode layers and cathode layers are arranged alternately in the cell stack along the stacking direction, the electrode layers each being separated from one another by separator layers are.

The method according to the invention is intended for producing a solid cell, in particular a cell component, such as a half, sandwich or mono cell or a mono cell stack, and is suitable and set up for this purpose. According to the method, at least two cell layers or cell layers are provided. In particular, at least one electrode layer and at least one separator layer are provided. According to the invention, a molten and ion-conductive adhesive is applied to at least one of the interfaces of the separator layer and/or the electrode layer. In particular, the adhesive is melted and applied to the interface in a liquid state.

The electrode layer and the separator layer are then arranged stacked one on top of the other, with the adjacent interfaces of the separator layer and the electrode layer being joined together in a materially bonded manner to form an ion-conductive adhesive bond (adhesive bond). The liquid adhesive is therefore hardened, whereby the separator layer and the electrode layer are mechanically and electrically connected in a materially bonded manner.

This creates a particularly suitable method for producing a solid-state cell. In particular, the process enables simple and reliable production of solid half, sandwich and mono cells, with the use of the molten and ion-conductive adhesive providing a particularly advantageous product constitution and product strategy for the production of pure solid cells.

According to the invention, the adhesive is only intended to ensure adhesion during assembly (stacking monocells). During later battery operation, re-melting of the adhesive is not critical, since the cell layers cannot slip against each other during a charging process in which the battery cell is charged with electrical energy and heats up in the process due to expansion (cell breathing) of the cell layers in the cell housing. The molten adhesive essentially only serves to make the production of the battery cell more efficient.

Preferably, half cells and monocells are first produced using the method, and then a monocell stack is produced as a cell stack of the solid cell from the monocells by direct stacking. This makes it possible to improve and increase efficiency in a cell construction line for solid-state cells.

In a conceivable embodiment, in particular the interface between a cathode layer and the separator layer is joined using the molten and ion-conductive adhesive. The anode sandwich cell can also be formed, for example, by a composite film made of separator/anode/separator.

A “material connection” or a “cohesive connection” between at least two interconnected parts is understood here and below in particular to mean that the interconnected parts at their contact surfaces through material combination or networking (for example due to atomic or molecular binding forces), if necessary under effect of an additive are held together.

Both the electrode layer and the separator layer have at least a certain surface roughness due to the manufacturing process. In a solid-state cell, however, it is necessary for good charge transport that the contact between the cell layers, in particular between the electrode layer and the separator layer, is as close as possible. Due to the roughness of the surfaces, however, it is often not possible to achieve complete surface contact between the two cell layers. In addition to better production design, the application of the ion-conductive adhesive also advantageously leads to a reduction in the interface resistance between the separator and the anode/cathode. Furthermore, the adhesive enables the compensation of unevenness in the interface, which in turn leads to improved homogeneity and thus to an increase in the electrochemical performance of the finished solid-state cell. The adhesive layer is made as thin as possible so that the volumetric capacity of the battery cell is not adversely reduced. For example, the applied adhesive layer has a layer thickness of between 0.1 µm (micrometers) and 10 µm.

In a preferred embodiment, the adhesive has ethylene carbonate (EC). In other words, an adhesive is used that has EC and is still able to conduct ions and join the necessary components (electrode layer/separator layer). EC has a comparatively low melting point, making it particularly easy to apply.

In a particularly preferred embodiment, EC is used as a molten adhesive. In other words, the adhesive is essentially formed by EC. The proportion of EC in the adhesive is greater than 50% by weight (weight percent), in particular greater than 75% by weight, for example greater than 90% by weight. EC has a melting point of 37 °C and is therefore particularly suitable for the process described above.

The advantages and refinements mentioned with regard to the method can also be transferred to the cell component according to the invention and vice versa. The cell component according to the invention is intended for the production of a solid cell and is suitable and set up for this purpose. The cell component has at least one electrode layer and at least one separator layer, the electrode layer and the separator layer being arranged stacked one above the other, and the electrode layer and the separator layer being joined to one another in a materially bonded manner at the mutually facing interfaces by means of a molten and ion-conductive adhesive bond. The cell component is in particular a unit or half cell of the solid cell. A particularly suitable cell component is realized by the adhesive connection according to the invention.

In an advantageous embodiment, the cell component is in particular designed as a mono-cell stack and has a number of electrode layers designed alternately as cathode and anode, which are arranged separately from one another with the interposition of a separator layer, the electrode layers and the separator layers each being made by means of a molten ion-conductive adhesive connection are cohesively joined together.

The solid cell according to the invention has a cell component described above. The statements in connection with the cell component also apply analogously to the solid cell and vice versa.

The solid-state battery according to the invention is intended for a motor vehicle and is suitable and set up for it. The solid-state battery is designed, for example, as a traction battery of an electrically driven or drivable motor vehicle, in particular an electric or hybrid vehicle.

• 1 eine Anoden-Halbzelle,
• 2 eine Anoden-Sandwichzelle,
• 3 eine Kathoden-Halbzelle,
• 4 eine Kathoden-Sandwichzelle,
• 5 eine Monozelle in einer ersten Ausführungsform,
• 6 eine Monozelle in einer zweiten Ausführungsform, und
• 7 unterschiedliche Ausführungen für einen Monozellenstapel.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. It shows in schematic and simplified representations:

• 1 an anode half cell,
• 2 an anode sandwich cell,
• 3 a cathode half cell,
• 4 a cathode sandwich cell,
• 5 a monocell in a first embodiment,
• 6 a monocell in a second embodiment, and
• 7 different versions for a mono cell stack.

Corresponding parts and sizes are always provided with the same reference numbers in all figures.

Below is based on the 1 to 7 a cell design according to the invention for solid-state cells is explained. According to the invention, the solid cell is assembled using prefabricated or preassembled cell components 2, 4, 6, 8, 10, 11. The cell components 2, 4, 6, 8, 10, 11 can be produced using a method according to the invention. The cell components 2, 4, 6, 8, 10, 11 are cell layer systems with a number of cell layers or cell layers.

The 1 shows a cell component 2 designed as an anode half cell.

In the in 1 In the embodiment shown, the anode half cell 2 has an electrode layer 12, in particular an anode layer, and a separator layer 14 joined thereto. The anode layer 12 has a film-like current conductor 16, which is coated on both sides with an active material 18, in particular an anode material. The interface 20 facing the separator layer 14 is joined and contacted in a cohesive manner with the separator layer 14 via an unspecified adhesive connection. For this purpose, during the production of the anode half cell 2, a molten and ion-conductive adhesive with ethylene carbonate is applied to the interface 20 and then bonded to the separator layer 14.

In the exemplary embodiment 2 the cell component 4 is designed as an anode sandwich cell. The anode sandwich cell 4 has two separator layers 14, between which the anode layer 12 is sandwiched. The anode layer 12 has two frontal or flat interfaces 20 in the area of the active material coating 18, which are joined to the respective associated separator layers 14 by the molten adhesive.

In the 3 a cell component 6 designed as a cathode half-cell is shown, which is designed to correspond to the anode half-cell 2. The cathode half cell 6 has an electrode layer 22 designed as a cathode layer instead of the anode layer 12. The cathode layer 22 has an active layer on both sides or cathode material 24 coated current collector 26. The cathode layer 22 or the surface of the cathode material 24 facing the separator layer 14 is joined and contacted in a materially bonded manner with the separator layer 14 at its interfaces 20 by means of a molten and ion-conductive adhesive connection.

The 4 shows a cell component 8 designed as a cathode sandwich cell, which is designed to correspond to the anode sandwich cell 4.

The half cells 2 and 6 form the smallest assembly or structural unit in the production of the solid cell, with the sandwich cells 4 and 8 being the next larger structural unit.

The half cells 2, 6 can be assembled to form a cell component 10, also referred to below as a monocell. The assembly of the half cells 2, 6 to form the monocell 6 is preferably carried out using the ion-conductive and molten adhesive. In other words, the electrode layers 12, 22 of one half cell 2, 6 are materially joined and contacted at the interface 20 with the separator layer 14 of the other half cell 6, 2. The 5 shows an anode/separator/cathode/separator monocell 6, and the 6 shows a separator/anode/separator/cathode monocell 6.

The cell stack of a solid-state cell or battery is preferably formed by a cell component 11 in the form of a mono-cell stack, in which the mono-cells 10 are directly stacked on top of one another in alternating fashion. The mono-cell stack 11 has at least two mono-cells 10. The monocells 10 are joined and contacted at the respective facing interfaces 20 using the ion-conductive and molten adhesive.

The 7 shows four different mono-cell stacks 11, which differ in terms of energy optimization Eopt. On the left side of the 7 Mono cell stacks 11 with low energy optimization Eopt are shown, with the one on the right 7 Mono cell stack 11 with high energy optimization Eopt are shown. The monocell stacks 11 are provided with reference numbers merely as examples.

The one starting from the left side of the 7 First mono-cell stack 11 has three mono-cells 10 stacked one above the other and cohesively joined to one another. With increasing energy optimization Eopt, one cell layer 12, 14, 22 is eliminated. The cathode layers 22 supply the necessary ions for the ion transport during operation of the battery cell. Since each cathode layer 22 is coated on both sides, the bottom or front cathode layer 22, which is not enclosed between two anode layers 12, would effectively not be used, so that this can be omitted to increase the energy optimization Eopt. The mono-cell stack 11 therefore preferably has an anode layer 12 on the front side. This reduces the number of ions, which subsequently also reduces the risk of plating.

The claimed invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived by the person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all of the individual features described in connection with the various exemplary embodiments can also be combined in other ways within the scope of the disclosed claims without departing from the subject matter of the claimed invention.

For example, cell components made up of combinations of half cells 2, 6 with sandwich cells 4, 8, which can be used as a structural unit for direct stacking for the mono-cell stack 11, are also conceivable.

Reference symbol list

2

Cell component, anode half cell

4

Cell component, anode sandwich cell

6

Cell component, cathode half cell

8th

Cell component, cathode sandwich cell

10

Cell component, monocell

11

Cell component, monocell stack

12

Electrode layer, anode layer

14

Separator layer

16

current arrester

18

Active material, anode material

20

interface

22

Electrode layer, cathode layer

24

Active material, cathode material

26

current arrester

Eopt

Energy optimization

Claims (7)

Process for producing a solid cell, - wherein at least one electrode layer (12, 22) and at least one separator layer (14) are provided, - wherein a molten and ion-conductive adhesive is applied to an interface (20) of the separator layer (14) and/or the electrode layer (12, 22), - wherein the electrode layer (12, 22) and the separator layer (14) are arranged stacked one above the other, and - wherein the interfaces (20) of the separator layer (14) and the electrode layer (12, 22) are joined together in a materially bonded manner to form an ion-conductive adhesive bond. Procedure according to Claim 1 , characterized in that an adhesive containing ethylene carbonate is used. Procedure according to Claim 1 or 2 , characterized in that ethylene carbonate is used as an adhesive. Cell component (2, 4, 6, 8, 10, 11) for a solid cell, comprising at least one electrode layer (12, 22) and at least one separator layer (14), the electrode layer (12, 22) and the separator layer (14) being one above the other are arranged stacked, and wherein the electrode layer (12, 22) and the separator layer (14) are cohesively joined to one another at the mutually facing interfaces (20) by means of a molten and ion-conductive adhesive bond. Cell component (10, 11). Claim 4 , comprising a number of electrode layers (12, 22) designed alternately as cathode and anode, which are each arranged separately from one another with the interposition of a separator layer (14), the electrode layers (12, 22) and separator layers (14) each being arranged by means of a molten and ion-conductive adhesive bond are joined together in a cohesive manner. Solid cell having a cell component (2, 4, 6, 8, 10, 11). Claim 4 or 5 . Solid-state battery for a motor vehicle, comprising a solid-state cell Claim 6 .

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